Ice cream containing a lactose enzyme composition and method

ABSTRACT

An enzyme--ice cream composition in which a sterilized acid-sensitive lactase enzyme hydrolyzes lactose after the ice cream is frozen to a temperature less than twenty degrees Fahrenheit.

This application is a CIP of application Ser. No. 08/707,732, filed Sep.3, 1996, now U.S. Pat. No. 5,707,843.

This invention relates to enzyme compositions.

More particularly, the invention relates to an enzyme composition whichcan be added to a pasteurized or sterilized dairy product withoutcontaminating the dairy product.

In another respect, the invention relates to a method which, incomparison to prior art procedures, significantly reduces the cost ofproducing reduced-lactose dairy products.

In a further respect, the invention relates to a method which continuesto reduce the lactose content of a dairy product after the dairy producthas been ingested.

In still another respect, the invention relates to a method whichinexpensively hydrolyzes all or part of the lactose in a dairy product.

In yet a further respect, the invention relates to an acidic compositionwhich is used to hydrolyze lactose in ice cream and which producesunexpected and surprising results by incorporating an acid sensitivelactose--hydrolyzing yeast enzyme to hydrolyze all of the lactose whenthe ice cream is frozen to less than twenty degrees fahrenheit.

Reduced-lactose content dairy products are well known and are utilizedby lactose intolerant individuals. Such products ordinarily are producedby one of two methods.

The first method for reducing the lactose content of a dairy productcomprises adding lactase enzyme to a milk product and then heating themilk product at an elevated temperature in excess of about 140 degreesFahrenheit for about three hours to allow the enzyme to hydrolyzelactose in the milk product. There are several disadvantages associatedwith this method. First, relatively large amounts of the lactase enzymeare required. The milk product typically must include 200 to 1000 partsper million of lactase enzyme. Lactase enzyme is costly. One gallon oflactase enzyme liquid costs about $65.00; one pound of solid lactaseenzyme costs about $120.00. Second, when the milk product is heated toan elevated temperature, the growth of unwanted bacteria and theproduction of off flavors can sometimes occur. Third, enzymes typicallyare laced with bacteria, exacerbating the growth of bacteria when themilk product is heated at an elevated temperature. Fourth, often only a70% reduction of the lactose to glucose and galactose is achieved by theenzyme.

The second method for reducing the lactose content of a dairy productcomprises adding lactase enzyme to a milk product and then cooling themilk product to below 45 degrees Fahrenheit for twelve to eighteen hoursto allow the enzyme to hydrolyze lactose in the milk product. There areseveral disadvantages associated with this method. First, relativelylarge amounts of the lactase enzyme are required. Lactase enzyme is, asnoted, costly. Second, maintaining dairy products at refrigeratedtemperatures is an added cost to any dairy operation. Third, often onlya 70% enzymatic reduction of the lactose to glucose and galactose isachieved during refrigeration of the dairy products. Fourth, the enzymetypically functions as a carrier which introduces foreign microbes intothe milk product.

Accordingly, it would be highly desirable to provide an improved methodand composition which would reduce the cost of enzyme, would reduceother costs associated with reducing the lactose content of a dairyproduct, and would achieve a significantly greater reduction of lactosethan prior art processing methods.

Therefore, it is a principal object of the invention to provide animproved composition and process for reducing the lactose in a dairyproduct.

A further object of the invention is to provide an improved foodcomposition which can, after a dairy product has been pasteurized orsterilized, be combined with a dairy product to reduce the concentrationof lactose in the dairy product.

Another object of the invention is to provide an improved foodcomposition and process which economically hydrolyzes lactose in a dairyproduct.

Still a further object of the invention is to provide an improved methodfor insuring the hydrolysis of all the lactose in a dairy product.

Yet another object of the invention is to provide an improved method forhydrolyzing lactose in a frozen shake dairy product while it is frozenfor storage, while it is being thawed to produce a milk shake which canbe ingested, and while the product is being ingested.

Yet still a further object of the invention is to provide an improvedmethod for commercially sterilizing an enzyme.

These and other, further and more specific objects and advantages of theinvention will be apparent to those skilled in the art from thefollowing detailed description thereof.

Briefly, I have discovered a chemical method to make a commerciallysterile powder enzyme composition for combination with alactose-containing liquid which has been heated to a selectedtemperature for a time sufficient to at least pasteurize thelactose-containing liquid. The enzyme composition hydrolyzes lactose toglucose and galactose and consists of from 4% to 20% by weight of anedible acid for adjusting the pH of the enzyme composition to within therange of about 2.0 to 6.0 when the composition is hydrated; from 2% to20% by weight of a buffering salt to facilitate maintenance of the pH inthe range of 2.0 to 6.0; from 0.02% to 10% by weight of an antimicrobialagent selected from the group consisting of sorbic acid, benzoic acid,sodium benzoate, potassium sorbate, sodium sorbate, and potassiumbenzoate; and, from 14% to 93% by weight of an enzyme to hydrolyzelactose. The enzyme powder composition can be hydrated and include from50% to 99% (preferably 79% to 98%) by weight of water. The pH of thehydrated enzyme food composition is from 1.5 to 6.0, preferably 2.0 toabout 4.6. For purposes of the present specification, the term "dairyproduct" is defined to include a liquid or solid food compositioncontaining lactose; and, the term commercially sterile means that apowder or liquid enzyme composition or a dairy product does not includeliving pathogenic bacteria, but may include living non-pathogenicbacteria. Pathogenic bacteria destroy healthy cells and prevent anindividual's body from functioning properly.

Any food grade emulsifier or wetting agent or surfactant can, ifdesired, be used in the powder enzyme composition for presentemulsification purposes and combinations for emulsifiers are used ifdesired. Any of the long fatty acid glycerol emulsifiers can be used,which normally have a C-12 to C-20 esterified chain. Typical among theseare glycerol-lactopalmitate or the stearate. Alternately, the propylenederived emulsifiers may be used, such as propylene glycomonosterate, oroleate, palmitate, and myristate. Likewise, the "Span" series ofemulsifiers may be used. These are well-known emulsifiers and are fattyacid partial esters of the sorbitol anhydrides (or sorbitan). One wellknown emulsifier is the "Tween" series of polyoxyethylene derivatives offatty acid partial esters of sorbitol anhydride. Tween 80 and Atmos 300are often used in combination. The well known Atmos series of mono anddiglycerides may be used. Also, lecithin is a suitable emulsifier orsodium lauryl sulfate is a suitable surfactant. The amount of theemulsifier is chosen to suit the particular powder enzyme composition,and generally ranges from about 0.01 % to 10% by weight.

The enzyme composition is provided in a powdered form which preferably,but not necessarily, has a relatively low moisture content. The moisturecontent is, as is the case for many powdered formulations, preferably atleast below 4% by weight and more preferably below 3% by weight. Suchlow moisture content provides a product having a shelf life of at leastone year shelf stability at ambient conditions if hermetically sealed.

The powdered form of the enzyme composition may be reconstituted with aliquid. The liquid form of the enzyme composition of the invention canbe heated to pasteurize or sterilize the composition, but need not be soheated because the hydrated enzyme composition is chemically sterilizedby the edible acid--buffer--antimicrobial agent combination.

As noted above, from 4% to 20% by weight of an edible acid is includedin the powder enzyme composition to adjust the pH of the enzymecomposition when the composition is hydrated. The edible acidulant can,for example, be malic acid, acetic acid, citric acid, lactic acid,sodium acetate, fumaric acid, or an acidic salt such as sodium acetatein order to adjust the pH within the range of 1.5 to 6.0, preferablyabout 2.0 to 4.6 when the powder composition is hydrated. This pH iscritical. Any pH in excess of about 6.0 is unacceptable because suchallows greater microbial activity and minimizes the antimicrobialeffects of sorbates and benzoates utilized in the invention. A pH equalto or less than 4.6 is preferred because the antimicrobial activity ofthe sorbates and benzoates is enhanced to insure, along with thebuffering salt, a chemically sterilized enzyme composition which issubstantially devoid of microbes.

From 2% to 20% by weight of a buffer, preferably a salt, in the powderenzyme combination functions to maintain the pH in the range of 2.0 to6.0. Examples of buffering salts include, by way of example and notlimitation, anhydrous disodium phosphate, dihydrated disodium phosphate,dipotassium phosphate, sodium citrate, potassium salts, calcium salts,and/or sodium salts.

From 0.02% to 10% by weight of an antimicrobial agent selected from thegroup consisting of sorbic acid, benzoic acid, sodium benzoate,potassium sorbate, sodium sorbate, and potassium benzoate functions incombination with the edible acid and buffering salt to produce anantimicrobial enzyme composition.

From 14% to 93% by weight of a lactose-hydrolyzing enzyme is included.By way of example, and not limitation, such enzymes can include lactase(fungal lactase for example), cellulase, and protease.

If desired, a powder filler like maltodextrin, or some othercarbohydrate can be utilized when preparing the enzyme powder of theinvention. The powder filler can comprise from 0.1% to 75% by weight ofthe enzyme powder composition. When a filler is added to the powderenzyme composition, it, as would be appreciated by those of skill in theart, proportionally reduces the weight percent of enzyme, acidulant,antimicrobial agent, and buffer salt in the food enzyme powdercomposition.

The powder enzyme composition is reconstituted with any desired edibleliquid, including, for example, an alcohol. The powder is ordinarilypartially dissolved and partially suspended in the resulting liquid formof the invention. The reconstituting liquid ordinarily will be water.

The antimicrobial activity of sorbic and benzoic acid is due primarilyto the undissociated acid molecule. Antimicrobial activity is thereforepH dependent and the estimated activity at any pH can be estimated asshown below in Table 1.

                  TABLE 1                                                         ______________________________________                                        EFFECT OF pH ON DISSOCIATION                                                             Percent Undissociated Acid                                         pH           Sorbic    Benzoic                                                ______________________________________                                        3            98        94                                                     4            86        60                                                     5            37        13                                                     6            6         1.5                                                    7            0.6       0.15                                                   ______________________________________                                    

Instead of chemically commercially sterilizing the lactose-hydrolyzingenzyme(s) utilized in the invention to selectively kill pathogenicbacteria while allowing other living bacteria to remain, the enzymecomposition can be commercially sterilized by filtering the compositionthrough a membrane with 0.45 microns openings to removed bacteria. Or,such a membrane filtration process can be utilized prior to combiningthe enzyme with the acidulant--buffer--antimicrobial agent chemicalsterilizing composition described above. One disadvantage of themembrane sterilization process is that the resulting sterilized enzymeruns the risk of contamination. In contrast, when the chemicalsterilizing composition described herein is utilized, the enzymes arecontinuously protected by that sterilizing composition until they areincorporated in a dairy product. Consequently, the chemicalsterilization composition of the invention is preferred.

In another embodiment of the invention, I have discovered a method forpreparing a pasteurized lactose-containing liquid in which theconcentration of lactose is decremented and which provides enzymes whichcontinue to function in the human digestive tract after ingestion of theliquid. The method includes the steps of providing a dairy product;providing a chemically commercially sterilized enzyme composition of thetype described above; heating the dairy product to a selectedtemperature for a time sufficient to at least pasteurize the dairyproduct; combining the chemically sterile enzyme composition with thepasteurized dairy product to produce an enzyme--dairy productcombination; packaging the enzyme--dairy product combination; and,storing the packaged enzyme--dairy product combination produced in step(e) to permit the enzyme to hydrolyze lactose in the enzyme--dairyproduct.

One advantage of the method of the invention is that a much smalleramount of enzyme can be utilized. Prior art processes typically requirefrom 200 to 1000 parts per million of enzyme for dairy products likewhole or skim milk, each of which contains about 4.5% by weight oflactose. Human milk contains about 10% by weight lactose. While theprocess of the invention can, if desired, utilize such highconcentrations of enzyme, ordinarily only 1 to 150 parts per million,preferably 5 to 75 parts per million, of enzyme is employed.

A second advantage of the method of the invention is that while priorart lactose reduction procedures ordinarily achieve only a seventypercent reduction of the lactose concentration in a dairy product, theprocess of the invention can achieve a one hundred percent reduction inthe lactose concentration. The lactose-hydrolyzing enzyme continues tofunction after the dairy product treated with the enzyme composition ofthe invention is packaged, after the dairy product is cooled or frozen(some product often continues to exist in the liquid state after theproduct is frozen, permitting the enzyme to continue gradually tohydrolyze lactose in frozen products), after the dairy product is, ifnecessary, thawed or warmed and served, and when the product isinitially introduced into the digestive tract of an individual. Theperiod of time required to hydrolyze substantially all of the lactose ina diary product for a given concentration in parts per million oflactose-hydrolyzing enzyme can be estimated quite accurately once thestorage temperature of the dairy product is known. For example, if thedairy product is whole milk and will be stored at 35 to 40 degreesFahrenheit, then, depending on the concentration of lactose-hydrolyzingenzyme, it may take from two to five days to hydrolyze substantially allof the lactose in the whole milk. If, on the other hand, the dairyproduct is a milk shake mixture which consists principally of milk andsugar and which may, for example, be refrigerated for twenty-four hours,frozen and stored for weeks or months at a temperature of abouttwenty-five degrees Fahrenheit, then, depending on the concentration oflactose-hydrolyzing enzyme, it may take from about three days to a weekor more to hydrolyze substantially all of the lactose in the milk shakemixture. As used herein, substantially all of the lactose in a dairyproduct is hydrolyzed when 98% or more of the lactose is hydrolyzed.

A third advantage of the method of the invention is that a dairy productneed not be heated or cooled for extended times immediately after theenzyme composition is added. Instead, normal processing procedures forthe dairy product can be continued. Heating the dairy product to apasteurization or sterilization temperature after the enzyme compositionis added is counterproductive in practicing the invention becauseenzymes are deactivated at pasteurization and sterilizationtemperatures. As used herein, a dairy product is deemed to be "at leastpasteurized" either if it is heated to a temperature for a timesufficient to pasteurize it or if it is heated to a temperature for atime sufficient to sterilize it.

A fourth advantage of the method of the invention is that it allows anenzyme to be added after the dairy product is pasteurized or sterilized.This is a particularly unusual aspect of the invention since the priorart teaches squarely against adding enzymes or other possiblecontaminants to a milk product after the milk product is pasteurized orsterilized. Buffers, acidulants, and benzoates or sorbates have beenlong utilized in a variety of food products, but apparently have neverbeen combined to chemically sterilize enzymes and produce a compositionwhich is introduced into a pasteurized dairy product to accomplishcomplete post-pasteurization lactose hydrolysis in accordance with themethod of the invention.

The pH stability of the enzyme composition of the invention is increasedby utilizing a buffer system. The buffer system resists any change inthe pH of the enzyme composition for one minute up to about three hours,preferably for at least about five to thirty minutes, after the enzymecomposition is hydrated to allow a sufficient period of time for atleast the pathogenic bacteria in the composition to be killed. Thebuffer system is important because the water utilized to hydrate theenzyme composition may include pathogenic bacteria or non-pathogenicbacteria. In particular, buffering salts are presently preferablypreferred in the practice of the invention and can, by way of exampleand not limitation, include anhydrous disodium phosphate, dihydrateddisodium phosphate, dipotassium phosphate, sodium citrate, potassiumsalts, calcium salts, and/or sodium salts.

The pH of the resulting hydrated enzyme composition is equal to or lessthan about 6.0, and under the most preferred conditions is less thanabout 4.6. The low pH has been found important in providing an enzymecomposition which has a high antimicrobial capacity and which can beadded to a pasteurized or sterilized milk product without microbiallycontaminating the milk product.

In another embodiment of the invention, I have discovered a method forcommercially sterilizing an enzyme. The method includes the steps offorming a chemical sterilization composition by admixing water, anedible acid, a buffer, and an antimicrobial agent selected from thegroup consisting of sorbic acid, benzoic acid, sodium benzoate,potassium sorbate, sodium sorbate, and potassium benzoate; and, mixingthe enzyme with the chemical sterilization composition to form an enzymesterilization composition. The enzyme sterilization composition has a pHin the range of 2.0 to 4.6 and includes 50% to 99% (preferably 79% to98%) by weight of water; 0.1% to 6.0% by weight of the edible acid;0.001% to 5.0% by weight of the buffer; 0.01% to 6.0% by weight of theantimicrobial agent; and, 0.001% to 45% (preferably 0.1% to 20%) byweight of the enzyme. The edible acid, buffer, and enzyme can be of thetypes earlier discussed herein.

In still a further embodiment of my invention, I have discovered animproved method for preparing and storing a pasteurizedlactose-containing liquid in which substantially all of the lactose ishydrolyzed prior to ingestion of the liquid by a lactose intolerantindividual. The method includes the steps of providing a dairy product;and, chemically commercially sterilizing a lactose-hydrolyzing enzyme byadmixing from 50% to 99% (preferably 79% to 98%) by weight of water,from 0.1 to 6% by weight of an edible acid for adjusting the pH of theenzyme composition within the range of about 2.0 to 6.0, from 0.001% to5% by weight of a buffer to facilitate maintenance of the pH in therange of 2.0 to 6.0, from 0.01% to 6% by weight of an antimicrobialagent selected from the group consisting of sorbic acid, benzoic acid,sodium benzoate, potassium sorbate, sodium sorbate, and potassiumbenzoate, and, from 0.001% to 45% (preferably 0.1% to 20%) by weight ofthe lactose-hydrolyzing enzyme to form a commercially sterile enzymecomposition. The dairy product is heated to a selected temperature for atime sufficient to at least pasteurize the dairy product; a selectedquantity of the commercially sterile enzyme composition is combined withthe pasteurized dairy product to produce an enzyme--dairy productcombination containing from five to one hundred and fifty parts permillion of said lactose-hydrolyzing enzyme; the enzyme--dairy productcombination is packaged; and, the packaged enzyme--dairy productcombination produced in step (e) is stored for a length of timesufficient to permit the enzyme to hydrolyze substantially all of thelactose in the enzyme--dairy product prior to ingestion of theenzyme--dairy product by an individual. The packaged enzyme--dairyproduct can be stored for a period of time in the range of two to sevendays, or longer, prior to ingestion. The edible acid, buffer, and enzymecan be of the types earlier discussed herein.

In yet another embodiment of my invention, I have discovered an improvedmethod for preparing and storing a pasteurized lactose-containing frozenshake product in which substantially all of the lactose is hydrolyzedprior to ingestion of the product by a lactose intolerant individual.The method includes the steps of providing a dairy product; and,chemically commercially sterilizing a lactose-hydrolyzing enzyme byadmixing from 50% to 99% (preferably 79% to 98%) by weight of water,from 0.1 to 6% by weight of an edible acid for adjusting the pH of theenzyme composition within the range of about 2.0 to 6.0, from 0.001% to5% by weight of a buffer to facilitate maintenance of the pH in therange of 2.0 to 6.0, from 0.01% to 6% by weight of an antimicrobialagent selected from the group consisting of sorbic acid, benzoic acid,sodium benzoate, potassium sorbate, sodium sorbate, and potassiumbenzoate, and, from 0.001% to 45% (preferably 0.1% to 20%) by weight ofthe lactose-hydrolyzing enzyme to form a commercially sterilized enzymecomposition. The dairy product is heated to a selected temperature for atime sufficient to at least pasteurize the dairy product; a selectedquantity of the commercially sterile enzyme composition is combined withthe pasteurized dairy product to produce an enzyme--dairy productcombination containing from five to one hundred and fifty parts permillion of the lactose-hydrolyzing enzyme; the enzyme--dairy productcombination is packaged and frozen such that said lactose-hydrolyzingenzyme continues to hydrolyze lactose after the product combination isfrozen; the packaged and frozen enzyme--dairy product combination isstored for a length of time sufficient to permit the enzyme to hydrolyzegenerally all lactose in the enzyme--dairy product combination prior toingestion of the enzyme--dairy product combination by an individual; theproduct combination is thawed until it has the consistency of aconventional ice cream milk shake containing ice particles in a liquidmatrix; and, the thawed product combination is served for ingestion byan individual. The packaged frozen product combination can be stored fora period of time in the range of two to fourteen days, or longer. Theedible acid, buffer, and enzyme can be of the types earlier discussedherein.

As would be appreciated by those of skill in the art, the amount ofwater admixed with a dried enzyme powder composition to produce awater--enzyme powder solution can vary widely as desired. Awater--enzyme powder solution can include 50% to 99% by weight water butpreferably includes from 79% to 98% by weight water.

In a further embodiment of my invention, I provide a method forpreparing a pasteurized lactose-containing ice cream product in whichlactose is hydrolyzed prior to ingestion of the product by a lactoseintolerant individual. The method includes the step of providing an icecream mix including from 5% to 70% by weight milk; from zero to 20percent by weight butterfat; from zero to fifty percent by weight cream;and, from one to seven percent by weight lactose. The method alsoincludes the step of chemically commercially sterilizing anacid-sensitive lactose-hydrolyzing lactase enzyme by admixing from 50%to 99% by weight of water; from 0.1 to 6% by weight of an acidiccomponent for adjusting the pH of the enzyme composition within therange of about 2.0 to 5.5; from 0.01% to 6% by weight of anantimicrobial agent selected from the group consisting of sorbic acid,benzoic acid, sodium benzoate, potassium sorbate, sodium sorbate, andpotassium benzoate; and, from 0.001% to 45% by weight of theacid-sensitive lactose-hydrolyzing lactase enzyme to form a chemicallysterile enzyme composition. The dairy product is heated to a selectedtemperature for a time sufficient to at least pasteurize the dairyproduct; a selected quantity of said chemically sterile enzymecomposition is combined with said pasteurized dairy product to producean enzyme--ice cream product containing from five parts per million toone thousand parts per million of said lactose-hydrolyzingacid-sensitive lactase enzyme; and, the enzyme--ice cream product ispackaged and frozen. The enzyme--ice cream product can be frozen to atemperature of less than minus twenty degrees Fahrenheit. The enzyme canbe a yeast-derived lactase enzyme; can continue to hydrolyze the lactosewhen the enzyme--ice cream product is at a temperature in the range ofminus forty to minus twenty degrees Fahrenheit; and/or, can hydrolyzesubstantially all of the lactose in the enzyme--ice cream product inabout three week. The chemically sterile enzyme composition is combinedwith the pasteurized dairy product within about ten minutes of admixingthe lactase enzyme with the water, the antimicrobial agent and theacidic component.

In another embodiment of my invention, I provide a commercially sterileenzyme powder composition for combination with an ice cream mix whichhas been heated to a selected temperature for a time sufficient to atleast pasteurize the ice cream mix. The enzyme composition hydrolyzeslactose to glucose and galactose. The enzyme composition includes from4% to 20% by weight of an edible acidic component for adjusting the pHof the enzyme composition with the range of about 2.0 to 5.5 when thecomposition is hydrated; from 0.02% to 10% by weight of an antimicrobialagent selected from the group consisting of sorbic acid, benzoic acid,sodium benzoate, potassium sorbate, sodium sorbate, and potassiumbenzoate; and, from 14% to 93% by weight of an acid-sensitivelactose-hydrolyzing lactase. The enzyme powder composition can behydrated and includes from 50% to 99% by weight of water.

In still a further embodiment of the invention, I provide an ice creamcomposition prepared to be frozen to hydrolyze lactose in thecomposition. The ice cream composition includes an ice cream mixincluding from 5% to 70% by weight milk; from zero to 20 percent byweight butterfat; from zero to fifty percent by weight cream; and, fromone to seven percent by weight lactose. The ice cream composition alsoincludes a sterilized lactose-hydrolyzing acid-sensitive lactase enzyme.The lactase enzyme can be admixed with the ice cream in a compositionincluding from 50% to 99% by weight of water; from 0.1 to 6% by weightof an acidic component for adjusting the pH of the enzyme compositionwithin the range of about 2.0 to 5.5; from 0.001% to 5% by weight of abuffer to facilitate maintenance of the pH in the range of 2.0 to 5.5;from 0.01% to 6% by weight of an antimicrobial agent selected from thegroup consisting of sorbic acid, benzoic acid, sodium benzoate,potassium sorbate, sodium sorbate, and potassium benzoate; and, from0.001% to 45% by weight of the lactase enzyme.

The following examples depict the presently preferred embodiments of theinvention for the purposes of illustrating the practice thereof and notby way of limitation of the scope of the invention. In the examples, allproportions are by weight, unless otherwise noted.

EXAMPLE 1

The following ingredients are provided.

    ______________________________________                                        Component                  Grams                                              ______________________________________                                        LACTASE ENZYME (1)         1000.00                                            CITRIC ACID 1 HYDRATE (ACIDULANT)                                                                        54.34                                              POTASSIUM SORBATE (ANTI BACTERIAL                                             AGENT)                     4.000                                              DISODIUM PHOSPHATE-DIHYDRATED (BUFFER)                                                                   36.819                                             SODIUM LAURYL SULFATE      .500                                               (SURFACTANT)                                                                  WATER (8.466 LB/GAL;                                                          3840 GM/GAL; 3.84 L/GAL)   14000.000                                          TOTAL                      15095.659                                          ______________________________________                                         (1) BetaD-galactosidase galactrohydrolase enzyme (I.U.B.3.2.1.23)             (hereafter "beta enzyme) from Solvay Enzymes, P.O. Box 4226, Elkhart,         Indiana 465140026.                                                       

The beta enzyme contains bacteria, as do many commercially availableenzymes. The water, potassium sorbate, disodium phosphate, and citricacid are blended together at room temperature to form a chemicalsterilization mixture. The beta enzyme is then mixed with the chemicalsterilization mixture to form a sterile enzyme composition. Theresulting sterile enzyme composition has a pH of 4.51. The pH stabilityof the enzyme composition of the invention is increased by utilizing abuffer system which resists any change in the pH of the composition. Inparticular, the disodium phosphate increases the pH stability of thecomposition. While any desired buffer system can be utilized in thepractice of the invention, sodium citrate, potassium salts, calciumsalts, and/or sodium salts are, by way of example and not limitation,presently preferred. The 4.51 pH of the resulting aqueous enzymecomposition is in the preferred pH range of 2.0 to 4.6.

EXAMPLE 2

Fifteen minutes after the hydrated enzyme composition of EXAMPLE 1 isproduced, a plate count is performed to determine the presence ofaerobic and anaerobic bacteria. The plate count is performed bytransferring one milliliter of the enzyme composition to a 10 milliliterenriched Thio. The Thio is incubated at 35° C. for four days to culturefor anaerobes. The Thio is then examined daily to determine theexistence of aerobic and anaerobic bacteria. The forgoing plate countprocedure is carried out in accordance with the FDA BacteriologicalAnalytical Manual, 4th Edition, 1984, Chapter 4, and with the ASM Manualof Clinical Microbiology, 4th Edition, 1985. In each plate count lessthan ten aerobic microorganisms (bacteria) per grams are detected. Noanaerobic bacteria are detected during any of the plate counts.

EXAMPLE 3

Fifteen minutes after the hydrated enzyme composition of EXAMPLE 1 isproduced, i.e., as soon as the rehydration of the powder is performed,about one milliliter of beta enzyme is extracted from the enzymecomposition. A plate count is performed to determine the presence ofaerobic and anaerobic bacteria. The plate count is performed bytransferring the one milliliter of beta enzyme to a 10 milliliterenriched Thio. The Thio is incubated at 35° C. for four days to culturefor anaerobes. The Thio is then examined daily to determine theexistence of aerobic and anaerobic bacteria. The forgoing plate countprocedure is carried out in accordance with the FDA BacteriologicalAnalytical Manual, 4th Edition, 1984, Chapter 4, and with the ASM Manualof Clinical Microbiology, 4th Edition, 1985. In each plate count lessthan ten aerobic microorganisms (bacteria) per grams are detected. Noanaerobic bacteria are detected during any of the plate counts.

EXAMPLE 4

Four thousand gallons of pasteurized whole milk is provided. The milkcontains about 4.5% by weight lactose. The 15095.159 grams of sterileenzyme composition from Example 1 is mixed with the 4000 gallons ofpasteurized whole milk at room temperature to form about 4000 gallons ofa milk--enzyme composition. The milk--enzyme composition is packaged inone gallon cartons. The one gallon cartons are refrigerated at 35 to 40degrees Fahrenheit.

EXAMPLE 5

Twenty-four hours after the milk in Example 4 is prepared and packaged,milk from one of the refrigerated one gallon cartons is tested todetermine the concentration of lactose. The milk contains about 3.0percent by weight lactose.

EXAMPLE 6

Forty-eight hours after the milk in Example 4 is prepared and packaged,milk from one of the refrigerated one gallon cartons is tested todetermine the concentration of lactose. The milk contains about 2.0percent by weight lactose.

EXAMPLE 7

Seventy-two hours after the milk in Example 4 is prepared and packaged,milk from one of the refrigerated one gallon cartons is tested todetermine the concentration of lactose. The milk contains about 1.0percent by weight lactose.

EXAMPLE 8

Ninety-six hours after the milk in Example 4 is prepared and packaged,milk from one of the refrigerated one gallon cartons is tested todetermine the concentration of lactose. The milk contains less than0.09% by weight lactose.

EXAMPLE 9

Examples 1 to 8 are repeated, except that the amount of citric acid inthe enzyme composition of Example 1 is decreased such that the pH of theresulting enzyme composition in Example 1 is about 5.1 instead of 4.51.Similar results are obtained.

EXAMPLE 10

Examples 1 to 8 are repeated, except that the amount of citric acid inthe enzyme composition of Example 1 is increased such that the pH of theresulting enzyme composition in Example 1 is about 2.6 instead of 4.51.Similar results are obtained.

EXAMPLE 11

Examples 1 to 8 are repeated, except that 500 grams of beta enzyme areutilized in the aqueous enzyme composition of Example 1 instead of 1000grams. Similar results are obtained except that the concentration oflactose determined in Examples 5 to 8 indicates that the lactoseconcentration is reduced more slowly than when only 454 grams of betaenzyme are utilized.

EXAMPLE 12

Examples 1 to 8 are repeated, except that fifty grams of disodiumphosphate are utilized to make the aqueous enzyme composition of Example1 instead of only 36.819 grams. Similar results are obtained.

EXAMPLE 13

Examples 1 to 8 are repeated, except that six grams of potassium sorbateis utilized to make the aqueous enzyme composition of Example 1 insteadof only two grams. Similar results are obtained.

EXAMPLE 14

Examples 1 to 8 are repeated, except that two grams of sodium sorbate isutilized to make the aqueous enzyme composition of Example 1 instead oftwo grams of potassium sorbate. Similar results are obtained.

EXAMPLE 15

Examples 1 to 8 are repeated, except that 36.819 grams of sodium citrateis utilized in place of 36.819 grams of disodium phosphate to make theaqueous enzyme composition of Example 1. Similar results are obtained.

EXAMPLE 16

Examples 1 to 8 are repeated, except that 54.346 grams of lactic acidare used in place of 54.346 grams of citric acid to make the aqueousenzyme composition of Example 1. Similar results are obtained.

EXAMPLE 17

Examples 1 to 4 are repeated, except that in Example 4 the sterileenzyme composition is mixed with four thousand gallons of a pasteurizedmilk shake dairy mixture instead of four thousand gallons of pasteurizedwhole milk. Mixing the enzyme composition and the milk shake dairymixture produces a milk shake--enzyme mixture. The pasteurized milkshake dairy mixture includes about 70% by weight whole milk; about 20%by weight sugar; about 7% by weight of a thickener like xanthan gum,locust bean gum, or guar gum; about 2% by weight of a stabilizer likemonodiglyceride; and, about one percent by weight of vitamins andminerals. The whole milk contains about 4.5% by weight lactose. Avariety of comparable formulations for making milk shake diary mixturesare well known in the art and will not be discussed in detail herein.Such mixtures, after being formulated, are typically refrigerated forten to thirty hours, are frozen during a two to three day period, andare stored for weeks or months before they are purchased and thawed toform a viscous partially frozen milk shake drink having a consistencycomparable to conventional vanilla or chocolate milk shakes sold by fastfood restaurants like MCDONALDS, DAIRY QUEEN, BURGER KING, etc.

The cartons of the milk shake--enzyme mixture are refrigerated fortwenty hours and are frozen by placing the cartons in a 25 degreeFahrenheit freezer for two to three days.

EXAMPLE 18

Twenty hours after the milk shake--enzyme mixture in Example 17 isprepared and packaged, and prior to its being frozen, milk shake--enzymemixture from one of the refrigerated one gallon cartons is tested todetermine the concentration of lactose. The milk shake--enzyme mixturecontains about 2.5 percent by weight lactose.

EXAMPLE 19

Since, as noted in Example 17, the one gallon cartons are placed in afreezer twenty hours after the milk shake--enzyme mixture in Example 17is prepared, the milk shake--enzyme mixture is partially frozenforty-eight hours following its preparation and packaging in Example 17.Forty-eight hours after the milk shake--enzyme mixture in Example 17 isprepared and packaged, partially frozen milk shake--enzyme mixture fromone of the one gallon cartons is tested to determine the concentrationof lactose.The partially frozen milk shake--enzyme mixture containsabout 2.0 percent by weight lactose.

EXAMPLE 20

Since, as noted in Example 17, the one gallon cartons are placed in afreezer twenty hours after the milk shake--enzyme mixture in Example 17is prepared, the milk shake--enzyme mixture is frozen seventy-two hoursfollowing its preparation and packaging in Example 17. Seventy-two hoursafter the milk shake--enzyme mixture in Example 4 is prepared andpackaged, frozen milk shake--enzyme mixture from one of the one galloncartons is tested to determine the concentration of lactose.The frozenmilk shake--enzyme mixture contains about 1.5 percent by weight lactose.

EXAMPLE 21

Since, as noted in Example 17, the one gallon cartons are placed in afreezer twenty hours after the milk shake--enzyme mixture in Example 17is prepared, the milk shake--enzyme mixture is still frozen one hundredand sixty-eight hours following its preparation and packaging in Example17. One hundred and sixty-eight hours (two weeks) after the milkshake--enzyme mixture in Example 17 is prepared and packaged, frozenmilk shake--enzyme mixture from one of the refrigerated one galloncartons is tested to determine the concentration of lactose. The frozenmilk shake--enzyme mixture contains less than about 0.05 percent byweight lactose.

EXAMPLE 22

Examples 17 to 21 are repeated, except that the amount of citric acid inthe enzyme composition of Example 1 (i.e., the enzyme composition usedin the milk shake--enzyme mixture of Examples 17 to 21) is decreasedsuch that the pH of the resulting enzyme composition in Example 1 isabout 5.1 instead of 4.51. Similar results are obtained.

EXAMPLE 23

Examples 17 to 21 are repeated, except that the amount of citric acid inthe enzyme composition of Example 1 (i.e., the enzyme composition usedin the milk shake--enzyme mixture of Examples 17 to 21) is increasedsuch that the pH of the resulting enzyme composition in Example 1 isabout 2.6 instead of 4.51. Similar results are obtained.

EXAMPLE 24

Examples 17 to 21 are repeated, except that 900 grams of lactase enzymeare utilized in the aqueous enzyme composition of Example 1 (i.e., theenzyme composition used in the milk shake--enzyme mixture of Examples 17to 21) instead of only 454 grams. Similar results are obtained exceptthat the concentration of lactose determined in Examples 18 to 21indicates that the lactose concentration is reduced more quickly thanwhen only 454 grams of lactase enzyme are utilized.

EXAMPLE 25

Examples 17 to 21 are repeated, except that fifty grams of disodiumphosphate are utilized to make the aqueous enzyme composition of Example1 (i.e., the enzyme composition used in the milk shake--enzyme mixtureof Examples 17 to 21) instead of only 36.819 grams. Similar results areobtained.

EXAMPLE 26

Examples 17 to 21 are repeated, except that six grams of potassiumsorbate is utilized to make the aqueous enzyme composition of Example 1(i.e., the enzyme composition used in the milk shake--enzyme mixture ofExamples 17 to 21) instead of only two grams. Similar results areobtained.

EXAMPLE 27

Examples 17 to 21 are repeated, except that two grams of sodium sorbateis utilized to make the aqueous enzyme composition of Example 1 (i.e.,the enzyme composition used in the milk shake--enzyme mixture ofExamples 17 to 21) instead of two grams of potassium sorbate. Similarresults are obtained.

EXAMPLE 28

Examples 17 to 21 are repeated, except that 36.819 grams of sodiumcitrate is utilized in place of 36.819 grams of disodium phosphate tomake the aqueous enzyme composition of Example 1 (i.e., the enzymecomposition used in the milk shake--enzyme mixture of Examples 17 to21). Similar results are obtained.

EXAMPLE 29

Examples 17 to 21 are repeated, except that 54.346 grams of lactic acidare used in place of 54.346 grams of citric acid to make the aqueousenzyme composition of Example 1 (i.e., the enzyme composition used inthe milk shake--enzyme mixture of Examples 17 to 21). Similar resultsare obtained.

EXAMPLE 30

Examples 1 to 8 are repeated, except that 1000 grams of lactase enzymeare utilized in the aqueous enzyme composition of Example 1 instead of1000 grams of beta enzyme. Similar results are obtained.

EXAMPLE 30

Examples 1 to 8 are repeated, except that 1000 grams of protease enzymeare utilized in the aqueous enzyme composition of Example 1 instead of1000 grams of beta enzyme. Similar results are obtained.

EXAMPLE 31

The following ingredients are provided.

    ______________________________________                                        Component               Pounds                                                ______________________________________                                        LACTASE ENZYME (Yeast derived)(1)                                                                     2.20                                                  CITRIC ACID 1 HYDRATE (ACIDULANT)                                                                     0.05                                                  POTASSIUM SORBATE (ANTI BACTERIAL                                                                     0.110                                                 AGENT)                                                                        WATER (8.466 LB/GAL;    42.000                                                3840 GM/GAL; 3.84 L/GAL)                                                      TOTAL                   44.365                                                ______________________________________                                         (1)Solvay Enzymes, P.O. Box 4226, Elkhart, Indiana 465140026. The lactase     enzyme is derived from the controlled fermentation of the yeast               Kluyveromyces lactis. Solvay Enzymes noted that this enzyme was acid          sensitive and was intended for use only at a pH between 6 and 8. It           recommended that the enzyme not be utilized at a pH below 6 because the       enzyme rapidly lost its effectiveness below a pH of 6. Solvay Enzymes als     predicted that the enzyme would not function when  #used as described in      this and the following examples to hydrolyze lactose.                    

The water, potassium sorbate, and citric acid are blended together atroom temperature to form a chemical sterilization mixture. The lactaseenzyme is then mixed with the chemical sterilization mixture to form asterile enzyme composition. The resulting sterile enzyme composition hasa pH of about 4.5. The pH stability of the enzyme composition of theinvention can, if desired, be increased by utilizing a buffer systemwhich resists any change in the pH of the composition. In particular,disodium phosphate would increase the pH stability of the composition.While any desired buffer system could be utilized in the practice of theinvention, sodium citrate, potassium salts, calcium salts, and/or sodiumsalts are, by way of example and not limitation, presently preferred.The 4.5 pH of the resulting aqueous enzyme composition is in the desiredpH range of 2.0 to 5.5, preferably 2.5 to 5.1, for sterile enzymecompositions utilized in preparing ice cream in accordance with theinvention. As used herein, ice cream comprises a frozen dairy productincluding 5% to 70% by weight milk (in either liquid or dry (powder)form), zero to 50% by weight cream, one to seven percent by weightlactose, zero to 20% by weight butterfat or other fat, and five to 35%by weight sugar. Ice cream can also, if desired, include stabilizers,flavoring, preservatives, and other components found in ice creamprepared in accordance with the prior art. Examples of ice cream includesherbet, ice milk, and ice creams including varying proportions ofbutterfat or other fat substitutes. The process described in thisExample 31 is one procedure for producing sterilized lactase enzyme.Sterilized lactase enzyme can also be produced by filtering the enzymeto remove bacteria and other contaminants.

EXAMPLE 32

Five minutes after the hydrated enzyme composition of EXAMPLE 31 isproduced, a plate count is performed to determine the presence ofaerobic and anaerobic bacteria. The plate count is performed bytransferring one milliliter of the enzyme composition to a 10 milliliterenriched Thio. The Thio is incubated at 35° C. for four days to culturefor anaerobes. The Thio is then examined daily to determine theexistence of aerobic and anaerobic bacteria. The forgoing plate countprocedure is carried out in accordance with the FDA BacteriologicalAnalytical Manual, 4th Edition, 1984, Chapter 4, and with the ASM Manualof Clinical Microbiology, 4th Edition, 1985. In each plate count lessthan ten aerobic microorganisms (bacteria) per grams are detected. Noanaerobic bacteria are detected during any of the plate counts.

EXAMPLE 33

Five minutes after the hydrated enzyme composition of EXAMPLE 31 isproduced, i.e., as soon as the rehydration of the powder is performed,about one milliliter of lactase enzyme is extracted from the enzymecomposition. A plate count is performed to determine the presence ofaerobic and anaerobic bacteria. The plate count is performed bytransferring the one milliliter of beta enzyme to a 10 milliliterenriched Thio. The Thio is incubated at 35° C. for four days to culturefor anaerobes. The Thio is then examined daily to determine theexistence of aerobic and anaerobic bacteria. The forgoing plate countprocedure is carried out in accordance with the FDA BacteriologicalAnalytical Manual, 4th Edition, 1984, Chapter 4, and with the ASM Manualof Clinical Microbiology, 4th Edition, 1985. In each plate count lessthan ten aerobic microorganisms (bacteria) per grams are detected. Noanaerobic bacteria are detected during any of the plate counts.

EXAMPLE 34

The following ingredients are mixed together to produce a vanilla icecream mix which has about 14% butterfat:

    ______________________________________                                        Component          Pounds                                                     ______________________________________                                        Milk, 3.25% butterfat                                                                            3731.000                                                   Cream, 40% butterfat                                                                             2800.350                                                   Milk (cow, dry, skim, non-fat)                                                                   240.030                                                    Cane Syrup         1155.700                                                   Corn Syrup         900.557                                                    Ultra High Stabilizer                                                                            26.670                                                     Artificial Vanilla Flavor                                                                        62.230                                                     ______________________________________                                    

EXAMPLE 35

The pasteurized vanilla ice cream mix of Example 34 is mixed togetherwith the enzyme composition of Example 31. The enzyme composition ofExample 31 is mixed together with the pasteurized ice cream mix ofExample 34 within about 10 minutes, preferably within about three tofive minutes, of adding the lactase enzyme to the chemical sterilizationmixture. If the lactase enzyme is permitted to remain in the chemicalsterilization mixture for more than about ten minutes, the lactaseenzyme may be inactivated. After the vanilla ice cream mix of Example 34is mixed together with the enzyme composition of Example 31, thefollowing enzyme--ice cream composition is produced:

    ______________________________________                                        Component                 Weight %                                            ______________________________________                                        Milk, 3.25% butterfat     41.6364                                             Cream, 40% butterfat      31.2508                                             Milk (cow, dry, skim, nonfat)                                                                           2.6786                                              Cane Syrup                12.8971                                             Corn Syrup                10.0498                                             Ultra High Stabilizer     0.2976                                              Artificial Vanilla Flavor 0.6945                                              LACTASE ENZYME (Yeast derived)(1)                                                                       0.0246                                              CITRIC ACID 1 HYDRATE (ACIDULANT)                                                                       0.0006                                              POTASSIUM SORBATE (ANTI BACTERIAL AGENT)                                                                0.0012                                              WATER (8.466 LB/GAL; 3840 GM/GAL; 3.84 L/GAL)                                                           0.4687                                              TOTAL                     100.0000                                            ______________________________________                                    

The enzyme--ice cream composition contains about 2.2% by weight lactose.After the enzyme--ice cream composition is prepared it is frozen at atemperature of minus forty degrees Fahrenheit. While the enzyme--icecream composition can be frozen at any temperature under thirty-twodegrees Fahrenheit, a freezing temperature of minus twenty degrees orless is preferred because at such low temperatures the size of icecrystals in the ice cream apparently is minimized.

EXAMPLE 36

One week after the enzyme--ice cream composition of Example 35 isfrozen, a small portion of the ice cream is tested to determine theconcentration of lactose. The ice cream contains about 1.8 percent byweight lactose.

EXAMPLE 37

Two weeks after the enzyme--ice cream composition of Example 35 isfrozen, a small portion of the ice cream is tested to determine theconcentration of lactose. The ice cream contains about 1.4 percent byweight lactose.

EXAMPLE 38

Three weeks after the enzyme--ice cream composition of Example 35 isfrozen, a small portion of the ice cream is tested to determine theconcentration of lactose. The ice cream contains no lactose. The lactosehas been completely hydrolyzed by the lactase enzyme. In view of thewarning by Solvay Enzymes that the yeast derived lactase enzyme wouldnot function, this was a surprising and unexpected result, both to theextent that the enzyme continued to hydrolyze lactose at such a lowtemperature and to the extent that the lactase enzyme completelyhydrolyzed the lactose in the ice cream. As used herein, anacid-sensitive enzyme is an enzyme the function of which is adverselyaffected when the enzyme is in a composition having an acidic pH.Acid-sensitive enzymes ordinarily at utilized in compositions having apH of 6.0 or greater, preferably 7.0 or greater.

EXAMPLE 39

Examples 31 to 38 are repeated, except that 2.20 pounds of a fungallactase enzyme derived by using aspergillus oryzae is utilized in placeof the 2.20 pounds of the yeast derived lactase. Similar results areobtained except that:

1. In Example 36, the ice cream contains 1.5% by weight lactose.

2. In Example 37, the ice cream contains 1.5% by weight lactose.

3. In Example 38, the ice cream contains 1.0% by weight lactose.

Consequently, while the acid sensitive yeast-derived lactase completelyhydrolyzed all of the lactose in three weeks, the fungal lactose didnot. This was another surprising and unexpected result because thefungal lactose is acid tolerant and is intended to be utilized incompositions having an acidic pH.

EXAMPLE 40

Examples 31 to 40 are repeated, except that the amount of citric acid inthe enzyme composition of Example 31 is decreased such that the pH ofthe resulting enzyme composition in Example 31 is about 5.1 instead of4.5. Similar results are obtained.

EXAMPLE 41

Examples 31 to 40 are repeated, except that the amount of citric acid inthe enzyme composition of Example 31 is increased such that the pH ofthe resulting enzyme composition in Example 1 is about 2.6 instead of4.5. Similar results are obtained.

EXAMPLE 42

Examples 31 to 40 are repeated, except that 1.1 pounds of lactase enzymeis utilized in Example 31 instead of 2.2 pounds. Similar results areobtained except that the concentration of lactose determined in Examples36 to 38 indicates that the lactose concentration is reduced more slowlythan when 2.2 pounds of lactase enzyme are utilized.

EXAMPLE 43

Examples 31 to 40 are repeated, except that 0.33 pounds of potassiumsorbate is utilized to make the sterile enzyme composition of Example 31instead of only 0.11 pounds. Similar results are obtained.

EXAMPLE 44

Examples 31 to 40 are repeated, except that 2.2 pounds of sodium sorbateis utilized to make the sterile enzyme composition of Example 31 insteadof 2.2 pounds of potassium sorbate. Similar results are obtained.

EXAMPLE 45

Examples 31 to 40 are repeated, except that 0.055 pounds of lactic acidare used in place of 0.055 pounds of citric acid to make the sterileenzyme composition of Example 31. Similar results are obtained.

EXAMPLE 46

Examples 31 to 40 are repeated, except that in Example 35 5731.35 poundsof milk with zero percent butterfat is utilized in place of the 3731.000pounds of milk having 3.25% butterfat and the cream having 40%butterfat. Similar results are obtained.

Having described my invention in such terms as to enable those skilledin the art to understand and practice it, and having identified thepresently preferred embodiments thereof, I claim:
 1. A method forpreparing a pasteurized lactose-containing ice cream product in whichlactose is hydrolyzed prior to ingestion of the product by a lactoseintolerant individual, said method including the steps of(a) providing adairy product comprising an ice cream mix including(i) from 5% to 70% byweight milk, (ii) from zero to 20 percent by weight butterfat, (iii)from zero to fifty percent by weight cream, and (iv) from one to sevenpercent by weight lactose; (b) commercially sterilizing alactose-hydrolyzing acid-sensitive lactase enzyme; (c) heating the dairyproduct to a selected temperature for a time sufficient to at leastpasteurize the dairy product; (d) combining a selected quantity of saidcommercially sterilized lactose-hydrolyzing lactase enzyme with saidpasteurized dairy product to produce an enzyme--ice cream productcombination containing from five parts per million to one thousand partsper million of said lactose-hydrolyzing lactase enzyme; (e) packagingand freezing said enzyme--ice cream product combination wherein saidenzyme--ice cream product is frozen to a temperature of less than minustwenty degrees Fahrenheit, and said enzyme continues to hydrolyze saidlactose at said temperature.
 2. The method of claim 1 wherein saidenzyme is a yeast-derived lactase enzyme.
 3. The method of claim 1wherein said enzyme is an acid sensitive lactase enzyme and said enzymecontinues to hydrolyze said lactose when said enzyme--ice cream productis at a temperature in the range of minus forty to minus twenty degreesFahrenheit.
 4. The method of claim 3 wherein said lactase enzymehydrolyzes substantially all of the lactose in said enzyme--ice creamproduct in about three weeks.
 5. The method of claim 1 wherein(a) saidlactase enzyme is sterilized by preparing a composition including(i)from 50% to 99% by weight of water, (ii) from 0.1 to 6% by weight of anacidic component for adjusting the pH of the enzyme composition withinthe range of about 2.0 to 5.5, (iii) from 0.01% to 6% by weight of anantimicrobial agent selected from the group consisting of sorbic acid,benzoic acid, sodium benzoate, potassium sorbate, sodium sorbate, andpotassium benzoate, and, (iv) from 0.001% to 45% by weight of saidlactase enzyme; and, (b) in step (d) said commercially sterilizedlactose-hydrolyzing lactase enzyme is combined with said pasteurizeddairy product within about ten minutes of admixing said acid sensitivelactase enzyme with said water, said antimicrobial agent, and saidacidic component.
 6. An ice cream composition prepared to be frozen tohydrolyze lactose in said composition, said composition including(a) anice cream mix including(i) from 5% to 70% by weight milk, (ii) from zeroto 20 percent by weight butterfat, (iii) from zero to fifty percent byweight cream, and (iv) from one to seven percent by weight lactose; and,(b) a sterilized lactose-hydrolyzing acid-sensitive lactase enzymewherein said lactase enzyme is admixed with said ice cream mix in acomposition including(I) from 50% to 99% by weight of water, (ii) from0.1 to 6% by weight of an edible acidic component for adjusting the pHof the enzyme composition within the range of about 2.0 to 5.5, (iii)from 0.001% to 5% by weight of a buffer to facilitate maintenance of thepH in the range of 2.0 to 5.5, (iv) from 0.01% to 6% by weight of anantimicrobial agent selected from the group consisting of sorbic acid,benzoic acid, sodium benzoate, potassium sorbate, sodium sorbate, andpotassium benzoate, and, (v) from 0.001% to 45% by weight of saidlactase enzyme.